Starter including one-way clutch and method of manufacturing clutch outer of one-way clutch

ABSTRACT

The starter includes a planetary type reduction gear device for reducing rotational speed of a motor, the planetary type reduction gear including a sun gear coupled to a shaft of the motor, planetary gears engaging with the sun gear and a planetary carrier outputting a revolutional motion around the sun gear of the planetary gears as a drive torque of the motor. The starter further includes a one-way clutch transmitting the drive torque from a side of a clutch outer thereof to a side of a clutch inner thereof through rollers disposed in cam chambers formed between the clutch outer and the clutch inner. The clutch outer is integral with the planetary carrier. The planetary carrier is integrally formed with planetary shafts rotatably supporting the planetary gears, and projecting pins projecting in the same direction as the planetary shafts. The planetary shafts are located inwardly of the cam chambers.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to Japanese Patent Application No.2008-33047 filed on Feb. 14, 2008, the contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a starter including a planetary geartype reduction gear device and a one-way clutch, and a method ofmanufacturing a clutch outer of the one-way clutch.

2. Description of Related Art

There is known a starter including a planetary gear type reduction geardevice and a one-way clutch, and having a structure in which planetaryshafts rotatably supporting planetary gears are disposed integrally witha planetary carrier, and the planetary carrier is integrated with aclutch outer of the one-way clutch. To manufacture such a clutch outerwith ease, it is known to use a cold forging process. However, the coldforging process has a problem that, since the cross-sectional area ofthe planetary shafts is small compared to that of the clutch outer, apressing force of a cam punch used to press a raw forging materialbecomes large. This may cause a mold used in the cold forging process tobe applied with stress large enough to damage the mold. As a techniqueto cope with this problem, it is known to integrate, in addition to theplanetary shafts, projecting pins projecting in the same direction asthe planetary shafts with the planetary carrier. For example, refer toJapanese Patent Application Laid-open No. 2004-301049.

However, the above technique has a problem in that since the planetaryshafts and the projecting pins are disposed outside cam chambers formedin the clutch outer, fluidity of the raw material to the planetary shaftand the projecting pins is lowered when the raw material is pressed bythe cam punch to form the cam chambers. That is, since it becomesdifficult for the raw material to flow into the holes made in the moldfor forming the planetary shafts and the projecting pins, the shaftdiameter of the planetary shafts may become non-uniform, and cracks mayoccur in the outer peripheral surface of the planetary shafts.

SUMMARY OF THE INVENTION

The present invention provides a starter comprising:

a planetary type reduction gear device for reducing rotational speed ofa motor, the planetary type reduction gear including a sun gear coupledto a shaft of the motor, planetary gears engaging with the sun gear anda planetary carrier outputting a revolutional motion around the sun gearof the planetary gears as a drive torque of the motor; and

a one-way clutch transmitting the drive torque from a side of a clutchouter thereof to a side of a clutch inner thereof through rollersdisposed in cam chambers formed between the clutch outer and the clutchinner;

the clutch outer being integral with the planetary carrier,

the planetary carrier being integrally formed with planetary shaftsrotatably supporting the planetary gears, and projecting pins projectingin the same direction as the planetary shafts,

the planetary shafts being located inwardly of the cam chambers.

The present invention also provides a method of manufacturing the clutchouter as described above by use of a cam punch for forming the camchambers, a concave die for defining a radially outer peripheral of theclutch outer and an axial end surface of the planetary carrier, theconcave die being formed with holes for forming the planetary shafts andholes for defining the projecting pins, and knockout pins inserted intothe holes for forming the planetary shafts to define axial end surfacesof the planetary shafts,

the method comprising the steps of:

setting a raw material in the die; and

molding the raw material by pressing the raw material by the cam punch,while pressurizing the knockout pins.

The present invention also provides a method of manufacturing the clutchouter as described above by use of a cam punch for forming the camchambers, a concave die for defining a radially outer peripheral of theclutch outer and an axial end surface of the planetary carrier, theconcave die being formed with holes for forming the planetary shafts andholes for defining the projecting pins, knockout pins inserted into theholes for forming the planetary shafts to define axial end surfaces ofthe planetary shafts, and an outer punch located around periphery of thecam punch, the method comprising the steps of:

setting a raw material in the die; and

molding the raw material by pressing the raw material by the cam punch,while pressurizing the outer punch and the knockout pins.

The present invention also provides a method of manufacturing a clutchouter of a one-way clutch included in a starter by a cold forgingprocess, the starter including:

a planetary type reduction gear device for reducing rotational speed ofa motor, the planetary type reduction gear including a sun gear coupledto a shaft of the motor, planetary gears engaging with the sun gear anda planetary carrier outputting a revolutional motion around the sun gearof the planetary gears as a drive torque of the motor; and

a one-way clutch transmitting the drive torque from a side of a clutchouter thereof to a side of a clutch inner thereof through rollersdisposed in cam chambers formed between the clutch outer and the clutchinner;

the clutch outer being integral with the planetary carrier,

the planetary carrier being integrally formed with planetary shaftsrotatably supporting the planetary gears, the planetary carrier having around hole formed at a radially center portion thereof,

the method comprising the steps of:

forming the planetary shafts inwardly of the cam chambers;

forming a projecting pin in a radially center portion of the planetarycarrier, the projecting pin projecting in the same direction as theplanetary shafts; and

forming the round hole to remove the projecting pin.

According to the present invention, it is possible to provide a starterin which planetary shafts integrally formed with a planetary carrierthereof have no cracks, and to provide a method of manufacturing aclutch outer integral with the planetary carrier of the starter in whichthe planetary shafts are uniform in diameter.

Other advantages and features of the invention will become apparent fromthe following description including the drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a cross-sectional view of a starter of an embodiment of theinvention;

FIG. 2A is an axial front view of an clutch outer of a one-way clutchincluded in the starter of the embodiment of the invention;

FIG. 2B is a cross-sectional view of the clutch outer taken along theline A-A in FIG. 2A;

FIG. 3 is a diagram showing a structure of a manufacturing apparatus formanufacturing the clutch outer shown in FIGS. 2A and 2B;

FIG. 4 is a cross-sectional view of a mold of the manufacturingapparatus in which a raw material is set;

FIG. 5 is a cross-sectional view of the mold during a molding process;

FIG. 6 is a cross-sectional view of the mold during the molding process;and

FIG. 7 is a cross-sectional view of the mold after completion of themolding process.

PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 is a cross-sectional view of a starter 1 according to anembodiment of the invention, FIG. 2A is an axial front view of a clutchouter 14 of a one-way clutch included in the starter 1, and FIG. 2B is across-sectional view of the clutch outer 14 taken along the line A-Aline in FIG. 2A. As shown in FIG. 1, the starter 1 includes a motor 2generating a torque, a reduction gear device 3 for reducing the rotationof the motor 2, an output shaft 4 disposed coaxially with an armatureshaft 2 a of the motor 2, a one-way clutch 5 transmitting the rotationof the motor 2 reduced by the reduction gear device 3 to the outputshaft 4, a pinion gear 6 coupled to the outer periphery of the outputshaft 4 by a helical spline, and an electromagnetic switch 8 which opensand closes a main contact of a motor circuit (not shown), and causes thepinion gear 6 to move in the direction opposite to the motor 2 through ashift lever 7. The starter 1 operates to start an engine (not shown) bytransmitting the torque generated by the motor 2 to a ring gear 9 of theengine through the pinion gear 6.

Next, the reduction gear device 3 and the one-way clutch 5 are explainedin detail below. The reduction gear device 3, which is a planetary geartype reduction gear device disposed coaxially with the armature shaft 2a of the motor 2, includes a sun gear 10 formed in one end of thearmature shaft 2 a, an annular internal gear 11 concentrically disposedwith the sun gear 10, a plurality of planetary gears 12 engaging withthe sun gear 10 and the internal gear 11, and a planetary carrier 13outputting the revolutional motion of the planetary gears 12. Theone-way clutch 5 includes the clutch outer 14 having an inner peripheryalong which cam chambers 14 a are formed (see FIGS. 2A and 2B), a clutchinner 15 rotatably disposed radially inwardly of the clutch inner 14,rollers 16 disposed on the outer periphery of the clutch inner 15 so asto be located in the cam chambers 14 a, and springs (not shown) forapplying biasing force to the rollers 16.

The planetary carrier 13, which is integral with the planetary carrier13, is integrally provided with three planetary shafts 17 rotatablysupporting the planetary gears 12, and three projecting pins 18projecting in the same direction as the planetary shafts 17 as shown inFIG. 2B. The planetary carrier 13 is formed with a round hole 13a at aradially center portion thereof. The planetary shafts 17 and theprojecting pins 18 are disposed inwardly of the cam chambers 14 a asshown in FIG. 2A. it is a matter of course that the projecting pins 18are located in such positions as not to interfere with the planetarygears 12 supported by the planetary shafts 17. Here, the phrase“inwardly of the cam chambers 14 a” means “inwardly of cam walls 14 bconstituting the outer peripheries of the cam chambers 14 (see FIG.2B)”, that is, within regions in which the axial thickness is formedthin by being pressed by a below described cam punch 19 duringmanufacture of the clutch outer 14.

Next, a method of manufacturing the clutch outer 14 is explained. Theclutch outer 14 is manufactured by a cold forging process using a belowdescribed manufacturing apparatus. As shown in FIG. 3, the manufacturingapparatus includes a mold constituted by the cam punch 19 for formingthe cam chambers 14 a, an outer punch 20 located around periphery of thecam punch 19, a concave die 22 for defining the radially outerperipheral of the clutch outer 14 and an end surface of the planetarycarrier 13, the concave die 22 being formed with holes 22 a and 22 b,and knockout pins 23 inserted into the holes 22 a. The manufacturingapparatus further includes a pressure generating device 21 forpressurizing the outer punch 20, and a pressure generating device 24 forpressurizing the knockout pins 23.

The outer punch 20 serves to define an axial end surface of the clutchouter 14 when the raw material 25 set in the die 22 is pressed by thecam punch 19. The knockout pins 23 serve to define an axial end surfaceof each of the planetary shafts 17 and the projecting pins 18 when theraw material 25 set in the die 22 is pressed by the cam punch 19. Theholes 22 a are formed at six positions corresponding to the threeplanetary shafts 17 and the three projecting pins 18 shown in FIG. 2A.On the other hand, the hole 22 b is formed at one position to form oneprojecting pin 18 at a radially center portion of the planetary carrier13 other than the above three projecting pins 18.

The clutch outer 14 is manufactured by performing the steps shown in theflowchart of FIG. 8. First, as shown in FIG. 4, a raw material 25 is setwithin the die 22 (step S10). Next, as shown in FIG. 5, the cam punch 19and the outer punch 20 are descended until they abut on the surface ofthe raw material 25 (step S20). Thereafter, the raw material 25 ispressed toward the die 22 by the cam punch 19 with the outer punch 20and the knockout pin 23 being applied with back pressure by the pressuregenerating devices 21 and 24 (step S30). As a result, as shown by thearrows in FIG. 6, the raw material flows to the outside of the cam punch19 and into the holes 22 a and 22 b. Subsequently, by descending the campunch 19 by a predetermined stroke to press the raw material 25 with theouter punch 20 and the knockout punch 23 being applied with the backpressure as shown in FIG. 7, the clutch outer 14 including the planetaryshafts 17 and the projecting pins 18 is obtained (step S40). Finally,the round hole 13 a is formed in the radially center portion of theplanetary carrier 13 to remove one of the projecting pins 18 which islocated in the radially center portion (step S50).

The above embodiment of the invention provides the following advantages.The clutch outer 14 manufactured by the above described process includesthe projecting pins 18 integrally formed thereto in addition to theplanetary shafts 17. Accordingly, since the cross sectional area of apassage through which the raw material flows increases, the pressingforce of the cam punch 19 can be reduced. This makes it possible toincrease the life of the mold, because the stress applied to the moldcan be reduced. Since the planetary shafts 17 and the projecting pins 18are located inwardly of the cam chambers 14 a, it is possible to apply auniform load to the cross-sectional area in the radial direction of eachof the planetary shafts 17 and the projecting pins 18 so that the rawmaterial flows uniformly. Furthermore, by pressurizing the outer punch20 and the knockout pins 23 during the molding process, the raw materialfillability to the planetary shafts 17 and the projecting pins 18 can beimproved. Hence, according to this embodiment, it is possible to formthe planetary shafts 17 and the projecting pins 18 which are uniform indiameter, and do not have cracks.

It is a matter of course that various modifications can be made to theabove embodiment as described below.

In the above embodiment, the outer punch 20 and the knockout pins 23 arepressurized when the raw material 25 is pressed by the cam punch 19. Theback pressures applied to the outer punch 20 and the knockout pins 23may be varied continuously over time, or in stages. For example, duringthe early stage of the molding process, the back pressure may be set toa larger value to generate a larger molding load in order for the crosssection of each of the planetary shafts 17 and the projecting pins 18 tobe a perfect circle, and during the medium stage of the molding process,the back pressure may be set to a smaller value to generate a smallermolding load in order for the planetary shafts 17 and the projectingpins 18 to extend sufficiently. During the final stage of the moldingprocess, the back pressure is set to a larger value again to generate alarger molding load in order to remove shear droop or sink marks.According to this modification, it is possible to improve the shapeaccuracy and height accuracy of the planetary shafts 17 and theprojecting pins 18. In addition, by reducing the back pressure duringthe medium stage of the molding process, it is possible to lengthen theplanetary shafts 17 and the projecting pins 18, and to increase the lifeof the mold because the pressing force applied to the mold becomessmaller. In the above embodiment, although the projecting pins 18 arelocated inwardly of the cam chambers 14 a together with the planetaryshafts 17, the above embodiment may be so modified that only theplanetary shafts 17 are located inwardly of the cam chambers 14 a, andthe projecting pins 18 are located outwardly of the cam chambers 14 a.

The above explained preferred embodiments are exemplary of the inventionof the present application which is described solely by the claimsappended below. It should be understood that modifications of thepreferred embodiments may be made as would occur to one of skill in theart.

1. A starter comprising: a planetary type reduction gear device forreducing rotational speed of a motor, said planetary type reduction gearincluding a sun gear coupled to a shaft of said motor, planetary gearsengaging with said sun gear and a planetary carrier outputting arevolutional motion around said sun gear of said planetary gears as adrive torque of said motor; and a one-way clutch transmitting said drivetorque from a side of a clutch outer thereof to a side of a clutch innerthereof through rollers disposed in cam chambers formed between saidclutch outer and said clutch inner; said clutch outer being integralwith said planetary carrier, said planetary carrier being integrallyformed with planetary shafts rotatably supporting said planetary gears,and projecting pins projecting in the same direction as said planetaryshafts, said planetary shafts being located inwardly of said camchambers.
 2. A method of manufacturing said clutch outer as described inclaim 1 by use of a cam punch for forming said cam chambers, a concavedie for defining a radially outer peripheral of said clutch outer and anaxial end surface of said planetary carrier, said concave die beingformed with holes for forming said planetary shafts and holes fordefining said projecting pins, and knockout pins inserted into saidholes for forming said planetary shafts to define axial end surfaces ofsaid planetary shafts, said method comprising the steps of: setting araw material in said die; and molding said raw material by pressing saidraw material by said cam punch, while pressurizing said knockout pins.3. The method according to claim 2, wherein pressure applied to saidknockout pins is varied during said molding step.
 4. A method ofmanufacturing said clutch outer as described in claim 1 by use of a campunch for forming said cam chambers, a concave die for defining aradially outer peripheral of said clutch outer and an axial end surfaceof said planetary carrier, said concave die being formed with holes forforming said planetary shafts and holes for defining said projectingpins, knockout pins inserted into said holes for forming said planetaryshafts to define axial end surfaces of said planetary shafts, and anouter punch located around periphery of said cam punch, said methodcomprising the steps of: setting a raw material in said die; and moldingsaid raw material by pressing said raw material by said cam punch, whilepressurizing said outer punch and said knockout pins.
 5. The methodaccording to claim 4, wherein pressures applied to said outer punch andsaid knockout pins are varied during said molding step.
 6. A method ofmanufacturing a clutch outer of a one-way clutch included in a starterby a cold forging process, said starter including: a planetary typereduction gear device for reducing rotational speed of a motor, saidplanetary type reduction gear including a sun gear coupled to a shaft ofsaid motor, planetary gears engaging with said sun gear and a planetarycarrier outputting a revolutional motion around said sun gear of saidplanetary gears as a drive torque of said motor; and a one-way clutchtransmitting said drive torque from a side of a clutch outer thereof toa side of a clutch inner thereof through rollers disposed in camchambers formed between said clutch outer and said clutch inner; saidclutch outer being integral with said planetary carrier, said planetarycarrier being integrally formed with planetary shafts rotatablysupporting said planetary gears, said planetary carrier having a roundhole formed at a radially center portion thereof, said method comprisingthe steps of: forming said planetary shafts inwardly of said camchambers; forming a projecting pin in a radially center portion of saidplanetary carrier, said projecting pin projecting in the same directionas said planetary shafts; and forming said round hole to remove saidprojecting pin.